code: def testWriteToString(self):
      file_path = os.path.join(self._base_dir, "temp_file")
      gfile._write_string_to_file(file_path, "testing")
      self.assertTrue(gfile.exists(file_path))
      file_contents = gfile._read_file_to_string(file_path)
      self.assertEqual("testing", file_contents)
  
imports: import os.path
  from tensorboard import test
  from tensorboard.compat.tensorflow_stub import compat, errors
  from tensorboard.compat.tensorflow_stub.io import gfile
label_desc: Use image node_id 4 for calling the FileIoTest obj's underlying member method code with example usage: obj.testWriteToString() without return types